1. Field of the Invention
The present invention relates to a wireless communication system, a wireless communication method, and a gateway, and more particularly to a wireless communication system such as a mobile communication system, a wireless communication method such as a mobile communication system, and a distributed gateway used in the wireless communication system such as the mobile communication system, which enhance a load distribution effect of a communication network.
2. Background Art
In general, a mobile communication system has a hierarchical structure. A WiMAX system will be described as an example of the mobile communication system having the hierarchical structure.
FIG. 23 is a diagram illustrating an outline of the WiMAX system.
The WiMAX system includes a mobile station (MS) 700, a base station (BS) 600, a BS 601, a BS 602, an access service network gateway (ASN-GW) 100 that manages the BSs, and a connectivity service network (CSN) 400. The CSN 400 has authentication, authorization, and accounting (AAA) related to accounting and authentication. Also, the CSN 400 has a home agent (HA) in a system that supports an IP. When the CSN 400 provides an internet service, the CSN 400 is connected to an internet 500.
The WiMAX system has a hierarchical structure in which the plurality of BS 600, BS 601, and BS 602 are connected to the ASN-GW 100 through a network 5002, a network 5003, and a network 5001. One of reasons that the mobile communication system has the hierarchical structure resides in the mobility realization of the MS 700. For example, let us consider a case in which the MS 700 travels from the BS 600 to the BS 601. The BS 600 of a travel source and the BS 601 of a travel destination are consolidated in the identical ASN-GW 100, to thereby realize handover in which the ASN-GW 100 detects the travel of the MS 700, and continues service.
FIG. 25 is a diagram illustrating a connection sequence of the WiMAX specified by WiMAX Forum of a standards body.
The MS 700, the BS 600, the ASN-GW 100, and the CSN 400 exchange messages with each other in conformity with the provision (800 to 821), and establish a radio path 822 between the MS 700 and the BS 600, and a generic routing encapsulation (GRE) capsuling path 823 between the BS 600 and the ASN-GW 100. When the MS 700 accesses to the internet, the MS 700 transmits user data to the BS 600 as radio data 7100. The BS 600 transfers the received user data to the ASN-GW 100 as GRE capsuling data 7101. Further, the ASN-GW 100 transfers the user data to the CSN 400, and the CSN 400 transfers the user data to the internet 500.
FIG. 26 is a diagram illustrating a GRE packet format of the GRE capsuling data between the BS and the ASN-GW. A GRE packet includes an IP header 7050, a GRE header 7051, and user data 7052. The user data 7052 is an IP packet transmitted by the MS 700. IP addresses of the BS 600 and the ASN-GW 100 are stored in the IP header 7050, and used as communication addresses of the BS 600 and the ASN-GW 100 which terminate a GRE tunnel. A GRE KEY specified in, for example, an RFC 2784 GRE and an RFC 1701 GRE is included in the GRE header 7051, and used to identify the MS 700.
In the mobile system thus stratified, the user data communicated by the MS 700 passes through the BS 600 via a radio zone as the radio data 7100, passes through the network 5002 and the network 5001 between the BS 600 and the ASN-GW 100, and arrives at the CSN 400 through the ASN-GW 100. The CSN 400 transfers the user data to the internet 500 according to routing.
FIG. 24 is a functional schematic diagram of the ASN-GW in the WiMAX system.
Also, the WiMAX Forum specifies that a function of the ASN-GW is divided into a function of processing signaling and a function of processing bearer data in a form illustrated in FIG. 24. A function unit for processing signaling is called “ASN-GW decision point 200”, and a function unit for processing the bearer data is called “ASN-GW enforcement point 300”.
As a related art, JP-A-2009-253678 proposes a method in which a load of a device is checked and allocated as an allocation method to the bearer data processing function.